MINERALOGICAL INVESTIGATION OF HISTORIC PGE TAILINGS OF AMANDELBULT MINE AND THEIR POTENTIAL

USE FOR CO2-SEQUESTRATION.

S.T. Lekgau and D.L. Reid Department of Geological Science, University of Cape Town, South Africa

Corresponding Author: Sefularo Tebogo Lekgaulkgsef001@myuct.ac.za

9th Inkaba yeAfrica Workshop GFZ – Potsdam, Germany

25 November 2012 – 1 December 2012

Introduction

25 – 30 November 20129th Inkaba yeAfrica Workshop – GFZ – Potsdam, Germany

• South Africa, annually produces 420 Million Mt of CO2.

• Several ways to curb CO2 emissions have been suggested: e.g. removing CO2 by mineral carbonation.

• S.A contains some of the largest potential mineral feedstock in the form of mine tailings from the primary beneficiation of PGE

• These materials are known to be rich in Ca-Mg-Fe bearing silicates.

Simplified geological map of the Bushveld Complex showing the locality

of Amandelbult Section. Source: bafokengplatinum.co.za

• This study focuses on the waste products of Amandelbult Platinum Mines – Dam 1.

• A relatively young operation owned by Anglo Platinum.

• Located in Limpopo Province, at the N end of the Western Limb within the RLS of the BC.

Objections

1. Characterize the mineralogy of the tailings from the point of view of possible recycling of the gangue material as a mineral reservoir for CO2.

325 November – 1 December 20129th Inkaba yeAfrica Workshop - GFZ Potsdam, Germany

2. Investigate the textural features such as particle size distribution and estimates of reactive surface area in order to calculate the capacity of Dam 1 to absorb CO2 in a carbonation reaction.

3. As contribution to recalculating residual PGE content, the relationship with grades and mineral properties established in (1) and (2) (above) was investigated.

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Results and Discussion

5

Surface area & Particle Size Distribution

ID Surface

area (m2/g)

TD 48 0.611

TD54 0.6812

TD 79 0.828

TD 4 1.0269

TD 45 1.1122

TD 3 1.1131

TD 15 1.2234

TD 69 1.2991

TD 50 1.349

TD 82 1.7574

TD 80 1.8513

TD 88 1.8604

1

Has an advantage of increasing the relative reactivity of the minerals. The sample ranged from 180µm-10µm and…………

Results and Discussion

6

Magmatic (%) Base metal sulphides (%) Alteration minerals (%) Chr 20.4 chalcopyrite 0.935 Hbl (Mg-Fe) 7.122 Opx 33.25 pyrite 0.386 Chl 4.071 Cpx 3.19 pentlandite 0.96 Cal 0.001 Bio 0.68 pyrrhotite 1.19 Epi 3.64 Plg 18.74 talc 1.33 Serp 3.89 Tot 76.26 Tot 3.47 Tot 20.05

No oli was found-but secondary minerals can be just as good ~ 68 % are carbonatable.

Mineralogy

Confirmed the presence of serp, cpx, plg, opx, chr but no talc nor oli peaks. All the samples produced similar peaks

Major Oxides TD69 TD15 TD50 TD45 TD3 TD4 TD48 TD54 TD88 TD82 TD80 TD79

SiO2 27.24 27.69 28.77 27.80 28.32 31.05 20.37 21.86 37.20 31.97 37.92 27.01TiO2 0.68 0.67 0.58 0.65 0.66 0.56 0.68 0.66 0.55 0.60 0.54 0.67Al2O3 11.87 12.14 13.18 11.88 11.69 12.18 14.04 13.40 12.39 11.64 12.17 11.96*FeO 19.84 19.94 18.76 19.34 19.63 17.90 22.14 21.55 15.58 17.68 15.41 19.92MnO 0.22 0.22 0.23 0.22 0.22 0.21 0.23 0.26 0.20 0.25 0.20 0.22*MgO 17.06 17.11 16.57 16.97 17.31 17.13 15.30 15.49 16.99 17.03 17.12 16.88*CaO 3.01 3.05 3.33 3.01 3.03 3.60 2.10 2.34 5.08 3.93 5.17 2.96Na2O 0.45 0.44 0.62 0.48 0.47 0.59 0.35 0.43 0.92 0.75 0.74 0.46K2O 0.08 0.09 0.11 0.08 0.09 0.10 0.07 0.13 0.14 0.12 0.15 0.09P2O5 0.04 0.04 0.04 0.04 0.04 0.04 0.03 0.05 0.04 0.04 0.04 0.04SO3 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.01 0.00 0.00Cr2O3 19.38 18.47 17.68 19.40 18.41 16.45 24.54 23.65 10.78 15.89 10.40 19.67NiO 0.13 0.13 0.13 0.13 0.13 0.17 0.14 0.16 0.11 0.12 0.11 0.13

Preferred oxides for mineral carbonation are marked with a (*)

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The 6-phase model from the mass balance calculations showed a significant amount of talc and opx components compared to the QXRD report & therefore unsatisfying

Results and DiscussionMineralogy

Chr dominated in the finer size fraction No correlation – chr not ore for platinum. No correlation – Ni not associated with sulphides

Conclusion

825 – 30 November 20129th Inkaba yeAfrica Workshop – GFZ – Potsdam, Germany

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